Ardour 5.8 stereo into mono drag drop

Thread 1 "ardour-5.8.65" received signal SIGSEGV, Segmentation fault.
0x0000555555aea4d6 in boost::shared_ptr<ARDOUR::Region>::shared_ptr (this=0x7fffffffbbc0, r=...)
    at /usr/include/boost/smart_ptr/shared_ptr.hpp:405
405	    shared_ptr( shared_ptr const & r ) BOOST_NOEXCEPT : px( r.px ), pn( r.pn )
(gdb) bt
#0  0x0000555555aea4d6 in boost::shared_ptr<ARDOUR::Region>::shared_ptr (this=0x7fffffffbbc0, r=...)
    at /usr/include/boost/smart_ptr/shared_ptr.hpp:405
#1  0x0000555555ae9ef4 in RegionView::region (this=0x0) at ../gtk2_ardour/region_view.h:66
#2  0x0000555555d7a519 in RegionMotionDrag::RegionMotionDrag (this=0x5555572fcdd0, e=0x55555a870b80, i=0x0, p=0x0, v=..., b=false)
    at ../gtk2_ardour/editor_drag.cc:632
#3  0x0000555555d81c41 in RegionInsertDrag::RegionInsertDrag (this=0x5555572fcdd0, e=0x55555a870b80, r=..., v=0x555562989d30,
    pos=19040) at ../gtk2_ardour/editor_drag.cc:1985
#4  0x0000555555d748ad in Editor::drop_regions (this=0x55555a870b80, x=56, y=612) at ../gtk2_ardour/editor_canvas_events.cc:1318
#5  0x0000555555d660a2 in Editor::track_canvas_drag_data_received (this=0x55555a870b80, context=..., x=56, y=612, data=...,
    info=0, time=72794659) at ../gtk2_ardour/editor_canvas.cc:372
#6  0x0000555555d7006b in sigc::bound_mem_functor6<void, Editor, Glib::RefPtr<Gdk::DragContext> const&, int, int, Gtk::SelectionData const&, unsigned int, unsigned int>::operator() (this=0x55555a8c1528, _A_a1=..., _A_a2=@0x7fffffffc0ac: 56,
    _A_a3=@0x7fffffffc0a8: 612, _A_a4=..., _A_a5=@0x7fffffffc0a4: 0, _A_a6=@0x7fffffffc100: 72794659)
    at /usr/include/sigc++-2.0/sigc++/functors/mem_fun.h:2469
#7  0x0000555555d6f7b1 in sigc::adaptor_functor<sigc::bound_mem_functor6<void, Editor, Glib::RefPtr<Gdk::DragContext> const&, int, int, Gtk::SelectionData const&, unsigned int, unsigned int> >::operator()<Glib::RefPtr<Gdk::DragContext> const&, int const&, int const&, Gtk::SelectionData const&, unsigned int const&, unsigned int const&> (this=0x55555a8c1520, _A_arg1=...,
    _A_arg2=@0x7fffffffc0ac: 56, _A_arg3=@0x7fffffffc0a8: 612, _A_arg4=..., _A_arg5=@0x7fffffffc0a4: 0,
    _A_arg6=@0x7fffffffc100: 72794659) at /usr/include/sigc++-2.0/sigc++/adaptors/adaptor_trait.h:194
#8  0x0000555555d6e7c9 in sigc::internal::slot_call6<sigc::bound_mem_functor6<void, Editor, Glib::RefPtr<Gdk::DragContext> const&, int, int, Gtk::SelectionData const&, unsigned int, unsigned int>, void, Glib::RefPtr<Gdk::DragContext> const&, int, int, Gtk::SelectionData const&, unsigned int, unsigned int>::call_it (rep=0x55555a8c14f0, a_1=..., a_2=@0x7fffffffc0ac: 56,
    a_3=@0x7fffffffc0a8: 612, a_4=..., a_5=@0x7fffffffc0a4: 0, a_6=@0x7fffffffc100: 72794659)
    at /usr/include/sigc++-2.0/sigc++/functors/slot.h:349
#9  0x00007ffff221d31d in ?? () from /usr/lib/x86_64-linux-gnu/libgtkmm-2.4.so.1
#10 0x00007ffff3526364 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#11 0x00007ffff3f66f75 in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#12 0x00007ffff3f79053 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#13 0x00007ffff3f81bcc in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#14 0x00007ffff3f8245b in g_signal_emit_by_name () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#15 0x00007ffff3657539 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#16 0x00007ffff3f66f75 in g_closure_invoke () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#17 0x00007ffff3f78f82 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#18 0x00007ffff3f81bcc in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#19 0x00007ffff3f8245b in g_signal_emit_by_name () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#20 0x00007ffff3585403 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#21 0x00007ffff3586d73 in gtk_selection_convert () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#22 0x00007ffff365a22e in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#23 0x00007ffff3658250 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#24 0x00007ffff3522b1b in gtk_main_do_event () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#25 0x00007ffff3196cdc in ?? () from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#26 0x00007ffff3c8d7d7 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
---Type <return> to continue, or q <return> to quit---
#27 0x00007ffff3c8da40 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#28 0x00007ffff3c8dd62 in g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#29 0x00007ffff3521a47 in gtk_main () from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#30 0x00007ffff74ef4f9 in Gtkmm2ext::UI::run (this=0x555557048740, old_receiver=...) at ../libs/gtkmm2ext/gtk_ui.cc:286
#31 0x00005555560945be in main (argc=1, argv=0x7fffffffd2c8) at ../gtk2_ardour/main.cc:447